Since ancient times iron production from iron ore made use of fuels such as coal or charcoal containing free carbon to produce the heat and reducing gases necessary for reduction of the ore. Wood alone produces much less heat, about 6,000-8,000 BTU/lb. compared with coal (12,000-15,000 BTU/lb) and coke (about 12,000-15,000 BTU/lb). In early times with small furnaces and simple air blowing equipment, the temperatures were not high enough to form iron carbide so the iron that formed initially was of little value and the ironmasters had to wait until the fire burned out to retrieve the “bloom,” a mass of 25-50 lbs. of iron containing little carbon that could be forged into weapons. Charcoal was used until about 1860 and after that coke produced from coal became the standard fuel for iron smelting. Coal consists largely of free carbon. Hard coal contains about 6% volatile matter and soft coal contains somewhat larger amounts of volatile matter. Coke has more free carbon and is made from coal by burning coal with restricted oxygen and maintaining the temperature of about 1,000° C.-1,300° C. to crack large molecules and drive off volatiles leaving the coke which has a higher mechanical strength and contains about 85-90% free carbon to provide the high temperatures required in iron smelting. In a modem furnace, alternate layers of iron ore, limestone and coke are placed in the furnace. Coke provides the heat required as well as the reducing gases necessary to convert the ore to metallic iron so that in a typical furnace 2,000 tons of iron ore (Fe3O4), 500 tons of coke and 400 tons of limestone will produce 1,000 tons of pig iron per day as well as 500 tons of slag and a large volume of combustible gas.
In the last few years methods have been developed for what is known as direct iron production; also referred to as the production of iron nuggets from iron ore as described for example in the following journal articles:    Kobayashi I., Tanigahi Y. and Uragami A, A New Process to produce Iron Directly From Fine Ore and Coal, Iron and Steelmaker, Vol. 28, No. 9, 2001, pp. 19-22.    Negami T., 2001, ITMK3 Premium Ironmaking Process for the New Millenium, Direct from Midrex 1st Quarter 2001.    Tsuge O., Kikukuchi S., and Tokuda K., Successful Iron Nugget Production at ITmk3 Pilot Plant, 61st Ironmaking Proceedings, Nashville, Tenn., 2002.    Anameric B. and Kawatra S. K., Laboratory Study Related to the Production and Properties of Pig Iron Nuggets, Minerals and Metallurgical Processing, Vol. 23, No 1, Feb. 2006 (a), pp. 52-56.    Anameric B., Rundman K. B. and Kawatra S. K. , Carburization Effects on Pig Iron Nugget Making, Minerals and Metallurgical Processing, Vol. 23, No 3, March 2006, pp. 139-151.    Anameric B. and Kawatra S. K., Pig Iron Nuggets Versus Blast Furnace Pig Iron, Presented at TMS Fall Extraction and Processing Meeting, Proceedings of the Sohn International Symposium, San Diego, Calif., Vol. 5, 2006 (b), pp. 136-156.    Anameric B. and Kawatra S. K., Conditions for Making Direct Reduced Iron, Transition Direct Reduced Iron and Pig Iron Nuggets in a Laboratory Furnace—Temperature Time Transformations, Submitted for publication in Minerals and Metallurgical Processing, May 2006 (c), Preprint no MMP-06-027.    Anameric B. and Kawatra S. K., Microstructural Investigation of the Pig Iron Nuggets Produced at Laboratory Conditions, ISIJ International, No 1, January 2007 (a).    Anameric B. and Kawatra S. K., Laboratory Scale Investigations on the Formation of Pig Iron Nuggets, Submitted for publications in ISIJ International, January 2007 (b).    Anameric B. and Kawatra S. K., Transformation Mechanisms of Self Reducing Fluxing Dried Greenballs into Pig Iron Nuggets, Presented at 2007 SME Annual Meeting, 2007 (c).
In these direct iron processes,coal is used as the reductant for the metal oxide. Up to the time of the present invention, commercial direct iron nugget smelting technologies depended upon coal as the reducing agent. To produce the necessary heat, traditional iron making technologies require either coke for blast furnaces or natural gas for direct reduced iron. As a fossil fuel, coal and natural gas is not sustainable in the long term and also leads to increasing levels of carbon dioxide in the atmosphere. Thus, prior to the present invention, it has been widely assumed that only fuels with at least as much energy content as coal were capable of producing the heat and the reducing gases necessary for reducing iron oxides to metallic iron nuggets. Consequently, heretofore only substances such as coal or coke containing large amounts of free carbon have been relied upon in the smelting process. However, besides being a limited nonrenewable resource, the burning of coal has caused environmental problems through the distribution of heavy metals such as mercury into the environment and the production of greenhouse gases which are widely acknowledged to be undesirable.
In view of these and other deficiencies in the prior art, it is one object of the invention to provide a new composition and method for the production of metallic iron from its ore that does not require charcoal, coal or coke yet allows the metal to be produced directly from the ore so that a metallic iron product can be produced for example in close proximity to the mine site allowing the metal to be marketed directly to numerous scrap remelters and other steel makers without passing through the traditional blast furnace process of iron production.
Another object is to produce metallic iron from its ore using renewable or recyclable materials without any kind of pretreatment of renewable materials such as the production of charcoal.
Still another object is to provide a direct iron process for producing metallic iron from its ore that constitutes an environmentally sustainable industry.
A more specific object is to provide a new composition and method for direct iron production wherein the reductant itself can act as the binder for holding a mass of material together without the requirement of an additive for this purpose.
Still another object of the invention is to provide a new composition and method for the production of metallic iron from its ore that results in less contamination of the finished product and smaller quantities of slag.
Yet another object is to provide a process of the type described in which the slag is readily separated from the metallic iron that is produced.
A further object is to provide an improved method and composition for the production of metallic iron which is stable against corrosion, can conveniently be shipped, is suitable feed stock for steel making either by remelting in electric furnaces or as replacement for scrap iron in the basic oxygen furnaces and that is able to employ a wide variety of readily available raw materials as well as other advantages and benefits that will be apparent from the following description.
These and other more detailed and specific objects of the invention will be apparent from consideration of the accompanying specification claims and drawings which illustrate by way of example but a few of the various ways in which the invention can be accomplished within the scope of the appended claims.